In general, dressings to be applied to various types of wounds, including burns and the like, should ideally promote healing, and provide protection, e.g. a bacterial barrier against infection and prevent pooling of wound exudate. While of lesser importance, they should be as comfortable as possible and not cause or contribute to ancillary problems such as bed sores and the like so common with patients bedridden for extended periods of time following surgery or treatment for burns and/or inflicted wounds. Moreover, they should ideally be transparent for visualization and monitoring of the underlying wound.
For convenience, such products will be referred to hereinafter throughout the specification and claims simply as "wound dressings".
Presently, there are essentially only two types of products commercially available for wound dressings, each of which affords certain advantages and, in turn suffers from certain disadvantages.
The first such product is a hydrogel such as "Vigilon" (trademark of C. R. Bard, Inc. for a non-adherent, breathable moist hydrogel which is inert, 96% water and 4% polyethylene oxide.) The Vigilon hydrogel provides a moist environment conducive to wound healing and granulation tissue formation as well as the absorption of wound exudate which would be inherent in the function of hydrogels in general. However, it is not highly absorbent and consequently requires fairly frequent replacement to obviate pooling of exudate and related problems. Moreover, since it is non-adherent to intact skin, it requires the use of adhesive tape for application to the skin as well as gauze or other covering means to prevent escape of the exudate. Apart from the time, trouble and expense of storing and assembling the materials needed to complete the wound dressing, bulky bandages frequently result, particularly where the wound covers a large or irregular surface area. This in turn may contribute to the further discomfort of the patient as well as bed sores from chafing and rubbing. Hydrogels such as Vigilon are disclosed for example, in U.S. Pat. Nos. 3,419,006, 3664,343 and 3,993,551.
For these and perhaps other reasons, a more commonly used product for wound dressings is "DuoDERM" (trademark of E. R. Squibb & Sons, Inc. for a dressing containing moisture-reactive particles surrounded by an inert, hydrophobic polymer.) The DuoDerm dressing has ah adhesive inner surface for application to the skin and wound and is said to be virtually impermeable to oxygen. As moisture enter the dressing, the moisture-reactive particles gradually swell, and dissolve to contain the accumulating exudate.
Wound dressings of the DuoDERM structure afford certain advantages, chief of which are the fact that they are unitary structures including the adhesive layer for securing the dressing, ease of application and the ability to contain exudate.
However, they possess certain significant disadvantages, e.g. the adhesive layer is a barrier to diffusion of exudate from the wound so that most of the fluid never diffuses through the adhesive layer; no transpiration of fluid to the atmosphere; the adhesive is aggressive to the intact perilesional skin so that on removal this skin may be traumatized; loss of adhesion in a day or two due to fluid accumulation; tends to exhibit an unpleasant odor when dissolved in wound fluid; and the oxygen-free environment provided by the oxygen- and water-impermeable outer surface provides a favorable environment at the wound locus for the growth of harmful anaerobic bacteria.
The above two products are in Applicant's judgement fairly representative of commercially available wound dressings. Others of course do exist. In addition, the patent literature is replete with references to various types of wound dressings.
While not intending to be a complete survey of the state of the art pertaining thereto, the following patents are nevertheless illustrative.
U.S. Pat. No. 3,249,109 issued to Maeth et al discloses a dressing including a flexible adhesive base composed of hydrated gelatin and including a small amount of pectin, and a fibrous backing member to prevent escape of materials from the base.
U.S. Pat. No. 3,800,792 issued to McKnight et al relates to a surgical dressing particularly useful for the treatment of burn wounds made from a collagen compressed foam film to which has been laminated, without any adhesive, a thin layer of an inert polymer such as polyurethane having a vapor transmission rate slightly higher than that of human skin.
U.S. Pat. No. 4,153,055 issued to Etes relates to a specified semisolid gel adapted for use in contact with the skin. Useful disclosed embodiments include a bandage wherein the gel layer has a fabric backing sheet on one side and a medical adhesive on the other.
U.S. Pat. No. 4,347,841 issued to Benyo et al discloses biological dressings for open wounds. In one embodiment (FIG. 2), the bandage comprises a gel-impregnated fabric having a protective outer layer on one side and a red cell concentrate plus gel former layer on the other side.
U.S. Pat. No. 4,367,732 issued to Poulsen is directed to a skin barrier which may be used for bandaging movable parts of the body, oonsisting essentially of a non-adhesive, substantially water-impervious elastic film, e.g. polyurethane film, coated with a specified gel-like, at least weakly elastic adhesive composition, the adhesive-coated film being characterized as having a low resistance to quick deformation, and after deformation, a rapid recovery to substantially it original shape.
U.S. Pat. No. 4,516,571 issued to Buchan relates to a device useful for the prophylaxis of pressure sores and which is removably attachable, comprising a mobile moisture-absorbing hydrophilic gel retained within a flexible elastomeric envelope, which envelope has a body contacting surface having a specified vapor transmission rate.
U.S. Pat. No. 4,541,426 issued to Webster disclosed a dressing comprising a conformable apertured film consisting of two layers laminated together, the first being the lesion-contacting layer formed from a material swellable on contact with water, the other either being non-swellable or swells less than the first layer. When in contact with a wet lesion, the different swell characteristics cause the apertures to open to allow passage of water. In the embodiment shown in FIG. 2, a layer of adhesive is provided for adhering to the skin; and in the embodiment of FIG. 3 an absorbent outer layer is present.
U.S. Pat. No. 4,552,138 issued to Hofeditz et al discloses dressings of at least one layer of a specified polymeric, hydrophilic gel, and where relevant, one or more layers of a carrier material as an intermediate and/or covering layer of woven or non-woven fabric or a foam.
Finally U.S. Pat. No. 4,556,056 issued to Fischer et al is directed to a transparent dressing material comprising a dry, swellable clear film of hydrophilic gel in the form of a sheet or strip and which may optionally contain a reinforcing mesh.
As previously stated, a wound dressing should ideally promote healing, provide protection for the wound and prevent pooling of wound exudate.
The present invention has for its task providing a wound dressing which provides all of these important functions and which at the same time is an integral composite structure which is both easy to apply to the wound and also contains all of the components essential for application and retention of the dressing to the skin.